This invention relates to an arrangement for using a line-scan television imager to produce television signals representative of a still image scene such as a scene produced by projecting a slide onto the surface of the imager.
It is often desirable to televise a still image. This may occur, for example, where a test image or test pattern is to be viewed for television receiver adjustments. More often, a television broadcaster may wish to broadcast television signals representative of one frame of a motion-picture film or a camera slide. It is known to use flying-spot scanners to generate a point light source which scans a rectangular raster. The scanning light source is projected through the slide onto a photosensitive detector to produce a time-varying signal in television format. The flying-spot scanner may be mechanically clumsy, because it uses a cathode ray tube to produce the moving point light source.
More recently, solid-state imagers such as charge-coupled devices (CCD) have been used in television cameras. A television signal representative of a still image can be generated with a two-dimensional CCD camera by projecting the image onto the photosensitive surface of the CCD imager, and reading out the television picture thus generated. While such two-dimensional CCD cameras are expected to become commercially practical in the future, the present state of the art makes it difficult to produce two-dimensional CCD imager arrays substantially without defects.
The manufacture of usable CCD arrays is made easier when the number of elements of the array is reduced. Consequently, in those applications in which it is possible, line-scan CCD arrays are used. A line-scan CCD array comprises a single line of photosensitive elements, and is thus a "one-dimensional" array. Being one-dimensional, such a linear array can generate a television signal representative of a two-dimensional scene only by relative motion between the image and the sensor. In the case of motion-picture film, the film may be kept in continuous motion whereby a moving image is generated at the surface of the line-scan sensor. Also, mirrors may be used to create a moving image as described in U.S. Pat. No. 4,205,337 issued May 27, 1980 to Millward. Such mirrors tend to be mechanically delicate and unsuited for hard use such as is encountered in broadcast studios. An improved arrangement for generating a television signal from a still image by the use of a line-scan sensor is desired.